I have a RRA 20" A2 with the 1:8 barrel.  There is a precision rifle class this weekend that I'd like to take, but I have no optics.  What'd work well on my handle?  The way I look at it I have two options: find someone that has what I want local (doubtful) or buy something cheap to get past the class, then get something cool later.

I'm thinking of building a flattop upper later as well.  Currently I'm looking at the Leupold M4 MRT and the Nightforce 2.5-10.  Don't really care for mil-dot reticles.

Also what type of rail/rings are suggested for on the handle?